The present invention relates to magnetic tape cassetes.
Heretofore, magnetic tape cassettes have been formed by combining upper and lower halves. In recording or reproducing signals, a magnetic tape wound on a pair of cores is run along the opening which is formed in the front side wall of the cassette, while being in contact with the magnetic head which extends into the opening.
If the upper and lower halves of the cassette are poor in flatness, then the perpendicularity of a guide member protruding into the cassette to guide the running of the tape is lowered, or the tape is shifted in its widthwise direction by the eccentricity of the winding cores. Thus, it is difficult to guide the tape correctly to the magnetic head; that is, the electromagnetic conversion characteristic is lowered.
For instance in a recording method using a PCM (pulse code modulation) digital audio system in which the displacement of the tape in its widthwise direction is strictly limited to record digital signals with high density, signals are recorded on the tape in multi-track manner. For this purpose, a system in which twenty to thirty-six tracks are formed on a tape for recording audio signals has been proposed. (Only four tracks are formed on a tape having the same width for recording stereo signals in the conventional analog system.) In the PCM system, signals are thus recorded on the tape with high density, for instance, with a track width of 100 .mu.m and an effective track pitch of 100 .mu.m. Accordingly, if the tape is displaced in its widthwise direction even slightly with respect to the magnetic head, then in recording or reproducing signals the same tracks are not traced. That is, a tracking error is caused, and it becomes considerably difficult to use different recording and reproducing apparatuses alternately in such a manner that signals are recorded by one of the apparatuses and are reproduced by another. In order to solve this problem, it is essential that the cassette have an excellent flatness property.
A magnetic tape cassette is well known in the art in which, in order to improve the flatness of the cassette, in place of the usual partition wall molded integrally with one of the upper and lower halves in such a manner as to protrude from the inner surface of the bottom of the half thereby to divide the hollow inside of the cassette into two parts, a partition wall is detachably arranged in the cassette (see Japanese Laid-Open Pat. Application No. 131817/1978).
That is, the halves, from which the partition wall for dividing the hollow inside of the cassette into a relatively small recording and reproducing region provided near the front opening of the cassette and a tape winding core accomodating region which is relatively large in area and is located behind the recording and reproducing region is formed, are molded so that the halves can be more accurately molded. The magnetic tape cassette is formed by fitting the partition wall between the halves.
A partition member is formed by extending pairs of guide walls from the front side of the partition wall.
The guide wall are so formed that they are perpendicular to the inner surfaces of the bottoms of the upper and lower halves, and the front ends thereof are used to guide the tape.
In the cassette designed as described above, the molded upper and lower halves are highly flat and the tape running characteristic is satisfactory.
However, the above-described cassette is disadvantageous in that, since the cassette has a plurality of openings in the front side wall the corresponding part of the metal mold must be of a so-called liner structure consisting of a number of blocks. Because of the structure of the metal mold, it is impossible to uniformly eject and cool the plastic resin. Especially the front parts of the halves are liable to be strained by molding, thus causing the halves to be somewhat poor in flatness.
The partition member having the partion wall is arranged near the front side wall of the cassette in such a manner that the top and bottom of the partition member are in close contact with the bottoms of the front parts of the upper and lower halves. Accordingly, when the upper and lower halves are combined together with screws, the partition member is affected directly by the strain of the upper and lower halves, as a result of which the perpendicularity of the partition member is lowered.
As the perpendicularity of the partition member is lowered, the perpendicularity of the protruding guide walls is also lowered. Accordingly, the tape, being supported by the front ends of the protruded guide walls, is run unstably.
An object of the invention is to provide a cassette in which the above-described difficulties accompanying a conventional cassette have been eliminated and which has partition member allowing the tape to run satisfactorily.